Chuck-key holder and safety device for power tools



Jan. 12, 1954 L. c. GRIFFIN 2,666,104

CHUCK-KEY HOLDER AND SAFETY DEVICE FOR POWER TOOLS Filed 001;. 25, 1951' IN V EN TOR. L AWRENCE' 6. GRIFFIN ATTORNEY Patented Jan. 12, 1954 UNITED STATES PATENT OFFICE CHUCK-KEY HOLDER AND SAFETY DEVICE FOR POWER TOOLS Lawrence C. Griflin, Akron, Ohio Application October 25, 1951, Serial No. 253,115

Claims. 1

This invention relates to improvements in power tools having key-operated chucks.

Heretofore, in the use of such power tools the usual turning keys for adjusting the tool chucks have frequently become misplaced or lost, thereby resulting in costly loss of time on the part of the operators of the tools, as well as the expense of replacing the keys. Moreover, such keys frequently caused injury to the hands of the operators, by being inadvertently retained in the chucks to revolve therewith after the power tools started to operate.

One object of the present invention is to provide a power tool of the type described wherein is incorporated improved means by which the tool cannot be operated unless the adjusting key is stored in a convenient and safe place, whereby is obviated the usual difficulties described above.

Other objects of the invention will be manifest from the following brief description and the accompanying drawings.

Of the accompanying drawings:

Figure 1 is a side elevation of a power hand drill embodying the features of the invention.

Figure 2 is a plan view of the chuck-key holder and safety device of the invention.

' Figure 3 is a cross-section taken substantially on the line 3-3 of Figure 1.

Figures 4 and 5 are vertical taken substantially on the lines respectively, of Figure 2.

Figure 6 is a wiring diagram illustrating the electrical connections between the drill motor and the safety device.

Referring to Figure l of the drawings the numeral ii) designates an electric hand drill of known type having the usual rotary chuck I for gripping a drill |2 or other cutting bit, the chuck having in the face thereof a socket |3 for reception of a reduced extension H on the shank l5 of a chuck key 5 t (see Figures 2 and 4), as shown in chain-dotted lines, in which position a bevel gear ll fixed on said shank meshes with a bevel gear It on a relatively rotatable part IQ of the chuck. A cylindrical pin or cross-arm 20 secured through the outer end of the shank provides freely extending handle portions 2|, 2| by which the key is manually turned to rotate the chuck part It with respect to chuck part 22, and thereby to tighten or loosen the grip on drill I2. The motor M (see Figure 6) may be connected to a suitable source of electric current by a cable 23.

In order to prevent operation of the hand drill while the key I6 is retained on the chuck II, a safety key-holder unit 24 is attached to cable 23 cross-sections, 4-4 and 5-5,

at a point remote from the hand drill, and in particular from the rotary parts thereof. Unit 24 may comprise a segmental casing formed of dielectric material, with two opposite parts or segments 26 and 2'! clamped together about the cable, as by means of bolts 28, 28. The segments have mating cavity portions 29, 29 providing a cavity 38, opening at opposite ends of the casing, in which is mounted a normally open switch 3|. This switch may include a metal clip 32, secured to the casing, on which is a fixed contact point 33, and a metal clip 34, also secured to the casing, from which extends an elongated springy con tact element 35 having its free end portion normally closely spaced from the fixed contact point 33. The cable 23 extends through the cavity 38, as shown in Figure 3, one Wire 37 thereof being continuous, while the other wire 38 is severed and bared to provide two ends which are connected to screws 39 and 40 on the metal clips 32 and 3 5, respectively. An elongated aperture 4| extending into the casing 24, in spaced relation to the cavity 38, is adapted to receive one or other of the handle extensions 2| of key IE to support the key when it is not in use, as shown in Figures 2 and 4. When an extension 2| is thus received in aperture 4| a member 42 of springy material, secured at one of its ends to casing part 26, is depressed to urge a slidably mounted pin or detent 43 of dielectric material in direction whereby a rounded head 44 on the detent yieldingly presses the switch element 35 into engagement with contact point 33. As long as the key is thus properly stored the switch will remain closed and permit operation of the drill motor M.

Secured to the end of casing part 26, intermediate the mouth of aperture 4| and the corresponding opening for cable 23, is a clip 45 of springy material, providing an arcuate tang 45 terminating in a reversely bent tip end. This clip is angularly disposed so that when a key handle 2| is inserted in aperture 4| as described, the shank |5 may be swung inwardly, yieldingly past said tip end, to be firmly releasably gripped in the stored position shown in Figures 2 and 4.

In use of the apparatus described the drill |il cannot be operated unless the key I6 is properly stored with one of its handle portions 2| inserted in the recess 4| of unit 24, as shown in Figures 2 and 4. Engagement of a handle portion 2| with springy member 42, through detent 43, holds springy element 35 in closed position against the contact point 33, thereby holding the circuit to motor M in readiness for operation of the drill,

to without departing from the spirit thereof or the scope of the appended claims As an exam-V ple, the safety key-holder unit- 24 may bein urit ed on a fixed structural part of a drill press or similar machine tool.

What is claimed is: V Y

1. A safety switch as for-use with a sewer tool requiring a separate chuck-locking key having an elongated projection thereon, comprising arelatively fixed casing Having a recess for slidably receiving a substantial liig'th' of said key proj ectioii therein to support the key on nieces: mg, switeheontacts iii saidcasinfg adapted to be in electrical connection to a said power tool, said switch contacts when" open preventing operation of the power tool, and switcfiafctuatinfgf me ns ifi said casing including a porti yieldin'gly em gageable by said key projection upon reception thereof in said recess-to close' said switch contacts and thereby permit operation of'the power tool.

2. A safety switch as :or use with a sewer 15001 requiring a sparateciiucradckisg key having an elongated prcjecticn thereon, comprising a; relatively fixed casing having a; recess for slid ably receiving a subs'tantial length of said projecticn therein to support the" on me casing switch ccfita'ets nsaid casing adapted to be in electrical connection to a said pawn-"tool; said switch contactswhen open preventing op? eration of the power tool; and actuatiri'g' means in said casing operable by reception of said key prnjectionm said recess-recluse said switch eontacts' and thereby permit cperaucs of the pews;- tool, said switcneontaets' ncluding a- Contact element yieldinglyhio'vable between" opened and closed pee said actuatmg means mun-ding es'ilient membe ex:

wer tool,-

4 the power means; and resilient switch actuating means in said switch casing including means extending into said recess and engageable by said key projection upon reception thereof in said recess to close said switch and thereby permit operation of the power means, means being provided on said switch casing for releasably retaining said key in said switch closed position thereof. v r

4. A safety switch as for use with a power tool requiring a separate chuck-locking key having an elongated projection thereon, comprising a relatively fixed casing having a recess for slidably receiving a substantial length of said key projection thereon to support the key on the casing, switch contacts in said casing adapted to r be in electrical connection to a said power tool,

(iii

said switch contacts when open preventing operationof the power tool, and switch actuating means in saidcasing including a portion yieldihgly engageable by said key projection upon reception said recess to close said switch contacts and thereby permit operation of the power tool, said electrical connection including an insulated electrical cablehaving wire connecti'ons to said switch contacts at a point remote from said power tool said Casing being segmental and having securing 'means for clamping the segments together to support the casing on the cable. H

5. A safety switch as for use with a power tool requiring a separate chuck locking key having an elongated projection thereon, comprising a relatively fixed casing having'a recess for longitudinally slidably receiving a substantial length of said key projection therein to support the key onfthe casing, switch contact means in said casin 'g" having electrical connection to a said power tool, said switch contact means when open preventing operation of the power tool, and switch actuating means in said casing including resilient means extending into said recess and yieldingly'engageable by said key projection upon reception thereof in said recess to close said switch contact means and thereby permit operation of the power tool, said electrical connection including an insulated electrical game having wire connections to said switch contact means to beat a point reinote'irom said power tool, said casing comprisingoppositesegmnts defining said aperture anda hollow portion containing said switch'contact means, and securingmeans being provided for clamping said segments together to support the casing on the'c'able.

LAWRENCE C. GRIFFIN. 

